Heat insulating cement



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Patented Feb. 28, 1933 V i UNITED STATES PATENT OFFICE LOUIS R. NICHOLS, F WESTON, MASSACHUSETTS HEAT INSULATING CEMENT No Drawing. Application filed March 21, 1931. Serial No. 524,413.

This invention relates to heat insulating gether upon wetting and allowing to set), or material, and pertains more particularly to asbestos-magnesia cement (a similar cement insulating cement suitable for application as containing finely divided magesiaz, plus a coating or covering to the exterior surfaces a small additional portion 0 or and ceof heating units, hot fluid conduits or conment, if desired. The flue soot and the cement tainers, such as steam boilers, hot water heatbinder are thoroughly intermixed so that ers, steam or hot water pipes, hot water tanks, the soot particles are distributed throughout or the like. the resulting substantially homogeneous com- The principal object of the invention is to position.

19 provide an improved material or composition Cementitious materials of this type are which is characterized by economy of procommonly used for insulation purposes in duction, ease of application, tenacity of adthe same manner as my composition is emhesion to coated surfaces of varying slope ployed; the material is applied while moist and contour, hardness of surface after apor wet and allowed to dry in the form of an.

15 plication, and especially its ability to reduce adhering coating, and its mode of application heat loss by conduction, convection or radiais consequently well understood. So far as tion through or from the applied coating. A I am aware, however, screened, flue soot has further and more specific purpose is to utilize never been used as an essential ingredient as an important ingredient of the composiof an insulating com osition of this class, and

tionaprevalent by-product of the combustion I have discovered t at a composition com- 7 of coal, coke or similar fuel, to wit soot which prising a relatively large proportion of soot is ordinarily discarded as wortmaste is not only considerably cheaper than the ormateriaL dinary asbestos cement insulation, but also The soot which I employ in preparing my furnishes a more satisfactory coating and com osition is deposited in the flues and possesses relatively higher insulating value. smo e pipes of the common coal boiler, heat- While the nature of the adhesive hinder or or furnace, and when removed from the Which is mixed with the soot, and the proheating unit, consists of finely divided, dust portions of the respective ingredients may like particles of carbon and contains the genbe varied within reasonable limits, as detera 0 eral insulating properties of lamp black. mined by experiment, for particular purposes,

Sometimes the soot upon being removed I have found that the following compositions from the heating unit is mixed with scale ash are satisfactory screened soot 70% b weight,

coal articles silica or dirt. In such cases, asbestos cement 25%, and Portlan cement prefer to sift and screen the mixture through '5 90 Soot 55%, asbesto cemen a, or a filter not coarser than twentymesh to the lanfi cement 5%; or soot 60%, asbestos ceinch, before compounding it with other inmenf 31 7 70; ort an cemen 2 0. n gredients to produce my improved insulation. eltlier of these formulae commercial asbestos- Although the screened soot itself will, when magnesia cements may be substituted for the 0 moistened, adhere to a hard surface as a thin common asbestos cements in the same propor- 4 film (probably because of a phenomenon of tion. Although a composition containing molecular attraction), it is necessary to mix 60% soot 37 a bestos-ma esia (85% it with a cementitious hinder or filler in order magnesla l, and fi Portland cement that a coating of the desired thickness will seemed most eflioient with re 1nstick to the surface to be insulated; and I 'sulating properties, I have found thatamix- I preferably use a binder which possesses fireture comprising 60% soot and 40% asbestosproof and heat insulating as well as adhesive ma nesia (50% magnesia; provedm properties. The binder may accordingly 1s ac ory for general use, for it adhered to comprise asbestos cement (a mixture of comthe coated surface better than the previous 50 minuted asbestos fibre and Portland cement composition and exhibited approximately the in sufiicms tom same insulating capacity, hardness and other desirable properties as the other combinations contemplated by this invention. It will be understood that the percentages above named are approximate only, and that the relative proportions of the materials may vary to a reasonable extent without impairin the results.

en this material was applied as a coating" approximately one inch thick, I found that the insulation adhered well and dried very hard without shrinking, cracking, or breaking away from the insulated surface upon drying; that its heat insulating characteristic was substantially higher than the usual asbestos, or asbestos-magnesia, cements and that it was fireproof and resistant to moisture absorption. The extreme hardness of the coatin rendersthe insulation more durable, as it is less likely to be torn, rubbed off, or otherwise damaged by external impacts; and also provides a substantially smooth exterior surface which may be painted if desired.

I attribute the success of my improved insulation to the following characteristics which are peculiar to the powdered soot constituting its major ingredient; its inherent nature as a mass of hard, finely divided carbon particles which when wet will closely adhere to a metal surface and to other ingredients of the composition and which when distributed through the coating provide air spaces which are relatively minute and hence tend to prevent internal circulation of heat; its low specific conductivity to heat (in the neighborhood of the insulation coeflicient of lampblack; and its capacity to withstand high temperatures without burning, melting or cracking. Hence, any suitable cementitious binder which is adapted tobemixed with the soot and to cooperate therewith in evincing or promoting its inherent properties, may be employed in the composition; and it will be understood that the soot is thoroughly mixed or distributed through the binding material to provide a substantially homogeneous composition which hardens upon drying to permit a dense, compact and substantially impervious coating.

The insulating composition is prepared and applied in the ordinary manner by adding water until the material is of a pasty or plaster-like consistenc and then spreading the moistened materia over the surface to be covered. Although the soot is less bul than a similar weight of asbestos cement, 1t will be found that the spreading capacity of my composition compares favorably with that of plain asbestos-cement, and that it is not necessary to employ forms or stays for holdingethe wet coating in place (as in the case of as stos-magnesia cement which does not stick readily and is diflicult to apply).

As above stated, a compositlon having a major proportion of soot is not only a better insulating material than the present commercial products but also substantially less expensive, for this by-product of combustion has heretofore had no commercial value. Indeed, it is quite common for householders and industrial plants to expend considerable sums for heater-cleaning service, and this expense would also be reduced if a commercial outlet for the removed soot were available. Obviously such service establishments provide a ready and economical source of supply for the soot which may be incorporated in my composition.

In my previous experiments I have used soot from anthracite coal, bituminous coal and coke and have obtained substantially equal results from all three types of combustible carbon products and it will be understood that my invention is not intended to be limited in respect to the source of the soot or to the particular materials herein described, except as the invention is defined in the following claims.

I claim:

1. A heat insulating composition capable of adhering to a metal surface while moist and of hardening thereon after drying, and consisting of a substantially homogeneous mixture of flue soot and a heat resistant, hydraulic cement.

2. A heat insulating composition capable of adhering to a metal surface while moist and of hardening thereon after drying, and consisting of a substantially homogeneous mixture of flue soot and an asbestos cement.

3. A heat insulating composition capable of adhering to a metal surface while moist and of hardening thereon after drying, and consisting of a substantially homogeneous mixture of at least fifty per cent., finely divided flue soot, and less than fifty per cent. asbestos-magnesia cement.

4. A heat insulating composition capable of adhering to a metal surface while moist and of hardening thereon after drying, and consisting of a substantially homogeneous mixture of screened flue soot and a heat resistant, hydraulic cement, the soot comprising finely divided particles capable of passing through a screen of twenty mesh to the inch and constituting more than fifty per cent. of the composition.

Signed by me at Boston, Massachusetts, this 19th day of March, 1931.

LOUIS R. NICHOLS. 

